President Trump on Wednesday raised the prospect of taking away credentials from news media outlets that he believes are reporting negatively on his administration, claiming that the “Fake News” is “working overtime” against him.

“Why do we work so hard in working with the media when it is corrupt?” Trump wrote on Twitter. “Take away credentials?”

The Fake News is working overtime. Just reported that, despite the tremendous success we are having with the economy & all things else, 91% of the Network News about me is negative (Fake). Why do we work so hard in working with the media when it is corrupt? Take away credentials?

Trump has long been critical of the news media, but taking away the credentials of White House reporters who cover him would take his animus to a new level.

In his tweet, Trump referred to a study that found 91 percent of network news stories about him are negative.

Shortly before, the hosts of “Fox & Friends” on Fox News discussed a study by the Media Research Center study citing that figure after evaluating the nightly newscasts on ABC, CBS and NBC between January and April.

There was also discussion on Fox & Friends” about the tone of the coverage of Trump’s announcement Tuesday that he is pulling the United States out of the Iran nuclear deal.

Later Wednesday, the president of the White House Correspondents Association said in a statement that if Trump were to carry out his threat, it would be “an unconscionable assault on the First Amendment.”

“Some may excuse the president’s inflammatory rhetoric about the media, but just because the president does not like news coverage does not make it fake,” said Margaret Talev, a White House reporter for Bloomberg. “A free press must be able to report on the good, the bad, the momentous and the mundane, without fear or favor.”

During his presidential bid, Trump’s campaign temporarily banned several news organizations from his rallies, including The Washington Post, citing dissatisfaction with the coverage.

If Trump were to deny White House credentials now that he’s president, it would be at odds with a pledge he made during a November 2015 interview with Time magazine.

Trump was asked: “Could you assure that even news outlets that you feel are being very unfair to you will continue to have their credentials at the White House if you’re elected President?”

Trump responded: “Oh yeah, I would do that. It doesn’t mean I’d be nice to them. I tend to do what I do. If people aren’t treating me right, I don’t treat them right.”

Revoking media credentials could restrict the ability of news organizations to report from the White House grounds, to attend press briefings and to travel with Trump on Air Force One.

The president’s tweets prompted an outcry on social media, including from Walter Shaub, the former director of the Office of Government Ethics.

In a tweet directed at Trump, he wrote: “’Take away credentials?’ These authoritarian impulses of yours are anti-American.”

Trump’s tweet was the second shot at the media in as many days from the White House. On Tuesday, Stephanie Grisham, communications director for Melania Trump, referred to the “opposition media” in a statement complaining about the focus of some of the coverage of the first lady’s rollout of an initiative to support children.